using System;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Xunit;
using Xunit.Abstractions;

namespace MyApp.Calculator;

public class CalculatorTests
{
    public CalculatorTests(ITestOutputHelper outputHelper)
    {
        OutputHelper = outputHelper;
    }

    private ITestOutputHelper OutputHelper { get; }

    [Fact]
    public void Calculator_Sums_Two_Integers()
    {
        // Arrange
        var services = new ServiceCollection()
            .AddLogging((builder) => builder.AddXUnit(OutputHelper))
            .AddSingleton<Calculator>();

        var calculator = services
            .BuildServiceProvider()
            .GetRequiredService<Calculator>();

        // Act
        int actual = calculator.Sum(1, 2);

        // Assert
        Assert.AreEqual(3, actual);
    }
}

public sealed class Calculator
{
    private readonly ILogger _logger;

    public Calculator(ILogger<Calculator> logger)
    {
        _logger = logger;
    }

    public int Sum(int x, int y)
    {
        int sum = x + y;

        _logger.LogInformation("The sum of {x} and {y} is {sum}.", x, y, sum);

        return sum;
    }
}